Symptom diagnosis: When the car is under heavy load, especially during driving bumps, it occasionally makes a knocking sound. It should be checked whether the balance axle of the rear axle is displaced and interferes with the drive shaft. If the noise increases with the increase of the vehicle speed during the operation of the car, and it is accompanied by jitter, this is generally caused by the loss of balance of the transmission shaft. This vibration is most noticeable in the cab. The unbalance of the dynamic balance of the transmission shaft should be less than 100 g. Cm. The failure of the dynamic balance of the transmission shaft will cause damage to related components. The most common are cracks in the clutch housing and fatigue damage in the middle rubber support.
Solution:
Plug the front wheel of the car tightly with a shim, and use jacks to lift the middle and rear drive axles on the side of the car; start the engine, put it on high gear, and observe the vibration of the drive shaft. Observe that when the speed drops during the inspection, if the pendulum vibration increases significantly, it means that the transmission shaft is bent or the flange is skewed.
The bending of the transmission shaft is the bending of the shaft tube, most of which is caused by the overload of the car. Due to overloading and overhanging of the car, the failure of the transmission shaft to bend or break frequently occurs. The drive shaft is seriously damaged due to overload and overhang. Although the intermediate support of the transmission shaft is strengthened and the strength of the flange fork is strengthened, the failure of breakage and damage still occurs.
After replacing the drive shaft components, after straightening, a balance check should be performed, and the unbalance amount should meet the standard requirements. The technical condition of the universal joint fork and the drive shaft hanger should also be checked in detail. For example, due to the unsatisfactory installation, the cross shaft and the roller damage will cause looseness and vibration, and the drive shaft will lose its balance.